The proposed research will use the pheochromocytoma clone PC12 as a model system for studying the role of S-adenosylmethionine-dependent methylation reactions in stimulus/secretion coupling. The first part of the work will study the effects of inhibitors of methyl transfer reactions on depolarization-dependent release of norepinephrine and acetylcholine from the cells. The second part of the work will determine if changes in rates of phospholipid and protein methylation occur during stimulation and if so, whether these changes are associated with depolarization, Ca ions influx, or neurotransmitter release. The effects of methyl transfer inhibitors on the incorporation of methyl groups into phospholipids and proteins also will be determined. The third phase of the study will determine if correlations exist between rates of lipid or protein methylation and cellular content of S-adenosylmethionine and S-adenosylhomocysteine. Finally, the enzymes and substrates required for methyl transfers to occur will be characterized using cell homogenates.